A gas compressor increases a pressure of a gas by reducing its volume. An air compressor is a specific type of gas compressor designed to compress air. Though a gas compressor and a fluid pump both increase the pressure on the gas/fluid and transport the gas/fluid through a conduit, a gas compressor also reduces the volume of the gas. Liquids are relatively incompressible. As a result, the main action of a pump is to pressurize and transport liquids and not to compress them. Gas compression is used in heating, ventilating, and air conditioning (HVAC) systems in buildings, cars, and airplanes, in vehicle propulsion, in energy storage, in air brakes in railway and road vehicles, in scuba diving equipment, in refrigeration systems, in air start systems for aircraft engines, etc. Gas compressors place significant demands on utility generators and power distributors.